Parasitic diseases may be caused by either endoparasites or ectoparasites. As used herein endoparasites refer to those parasites living inside the body of the host, either within an organ (such as the stomach, lungs, heart, intestines, etc.) or simply under the skin. Ectoparasites are those parasites that live on the outer surface of the host but still draw nutrients from the host. Endoparasitic diseases may further be subdivided based on class of parasite involved in the infection. For example, endoparasitic diseases generally referred to as helminthiasis are due to infection of the host with parasitic worms known as helminths. Helminthiasis is a prevalent and serious worldwide economic problem involving infection of domesticated animals such as swine, sheep, horses, cattle, goats, dogs, cats, and poultry. Many of these infections, caused by the group of worms described as nematodes, cause diseases in various species of animals throughout the world. These diseases are frequently serious and can result in the death of the infected animal. The most common genera of nematodes infecting the animals referred to above include, but are not limited to, Haemonchus, Trichostrongylus, Ostertagia, Nematodirus, Cooperia, Ascaris, Bunostomum, Oesophagostomum, Chabertia, Trichuris, Strongylus, Trichonema, Dictyocaulus, Capillaria, Heterakis, Toxocara, Ascaridia, Oxyuris, Ancylostoma, Uncinaria, Toxascaris, and Parascaris. Many parasites are species specific (infect only one host) and most also have a preferred site of infection within the animal. Thus, Haemonchus and Ostertagia primarily infect the stomach while Nematodirus and Cooperia mostly attack the intestines. Other endoparasites reside in the heart, eyes, lungs, blood vessels, and the like while still others are subcutaneous parasites. Helminthiasis can lead to weakness, weight loss, anemia, intestinal damage, malnutrition, and damage to other organs. If left untreated these diseases can result in the death of the animal.
Examples of endoparasites which infect animals and man include but are not limited to gastro-intestinal parasites of the genera Ancylostoma, Necator, Ascaris, Strongyloides, Trichinella, Capillaria, Trichuris, Enterobius, and the like. Other endoparasites which infect animals and man are found in the blood or in other organs. Examples of such parasites include but are not limited to filarial worms Wuchereria, Brugia, Onchocerca, and the like as well as extra-intestinal stages of the intestinal worms Strongylides and Trichinella. Ectoparasites which infest man and domestic animals include arthropods, such as ticks, fleas, mites, mosquitos, lice, and the like and infections by these parasites can result in transmission of serious and even fatal diseases.
Infestations by ectoparasitic arthropods including but not limited to ticks, mites, lice, stable flies, hornflies, blowflies, face flies, fleas, mosquitoes and the like are also a serious problem. Infection by these parasites results not only in loss of blood and skin lesions, but also can interfere with normal eating habits thus causing weight loss. Ectoparasitic infestations of a host can also result in transmission of serious diseases including but not limited to encephalitis, anaplasmosis, babesiosis, rocky mountain spotted fever, lyme disease, ehrlichiosis, West Nile virus, swine pox, malaria, yellow fever, and the like, many of which can be fatal to the host. Animals may be infected by several species of parasite at the same time since infection by one parasite may weaken the animal and make it more susceptible to infection by a second species of parasite.
Many of the compounds used in this invention are also active against household pests including but not limited to cockroach, Blatella sp., clothes moth, Tineola sp., carpet beetle, Attagenus sp. and the housefly Musca domestica and against Solenopsis invicta (imported fire ants), termites, and the like.
These compounds are furthermore useful against agricultural pests such as aphids (Acyrthiosiphon sp.) locusts, and boll weevils as well as against insect pest which attack stored grains such as Tribolium sp. and against immature stages of insects living on plant tissue. The compounds are also useful as a nematodicide for the control of soil nematodes, which may be agriculturally important.
Antiparasitic agents are also useful for the treatment and/or prevention of helminthiasis in domestic animals such as cattle, sheep, horses, dogs, cats, goats, swine, and poultry. They are also useful in the prevention and treatment of parasitic infections of these animals by ectoparasites such as ticks, mites, lice, fleas, mosquitoes and the like. They are also effective in the treatment of parasitic infections of humans.
Various methods of formulating antiparasitical formulations are known in the art. These include oral formulations, baits, dietary supplements, powders, shampoos, etc. Formulations for localized topical applications of antiparasitical formulations are also known in the art. For example, pour-on solutions comprising 1-N-phenylpyrazole derivatives, such as fipronil, are known in the art and are described in, for example, U.S. Pat. No. 6,010,710, U.S. Pat. No. 6,413,542, U.S. Pat. No. 6,001,384, U.S. Pat. No. 6,413,542 as well as copending application Ser. No. 10/120,691, filed Apr. 11, 2002 and now allowed. Other methods of formulating antiparasitic agents include spot-on formulations or sprays.
Spot-on formulations are well known techniques for topically delivering an antiparasitic agent to a limited area of the host. For example, U.S. Pat. No. 5,045,536 describes such formulations for ectoparasites. Other spot-on formulations include U.S. Pat. No. 6,426,333 and U.S. Pat. No. 6,482,425 and application U.S. Ser. No. 10/155,397, now allowed and published as Publication No. U.S. 2003-0050327A1. Reference is also made to Publication No. U.S. 2003-166688A1. WO 01/957715 describes a method for controlling ectoparasites in small rodents as well as interrupting or preventing the diseases caused by arthropods or small rodents, which comprise applying topical formulations, such as spot-on compositions, to the skin, or hair of the rodents.
1-N-arylpyrazoles as a class of chemicals are well known in the art, as well as methods for their use in controlling parasites including insects, such as fleas, ticks, lice or mosquitoes in mammals, such as domesticated livestock or companion animals or birds, either alone or in combination with other pesticides such as insect growth regulators. See, e.g., EP-A-295,217, EP 295 177, EP-A-840-686, EP-A-352,944, WO 00/35844, WO 98/39972, U.S. Pat. Nos. 5,122,530 5,236,938, 5,232,940, 5,576,429 5,814,652, 5,567,429, 6,090,751 and 6,096,329 as well as Publication No. US 2002-90381-A1. See also copending application U.S. Ser. Nos. 07/719,942; 08/933,016; 09/174,598; 08/863,182; and 08/863,692. The compounds of the families defined in these patents are extremely active and one of these compounds, 5-amino-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-trifluoromethylsulfinylpyrazole, or fipronil, is particularly effective, but not exclusively effective, against fleas and ticks. The 1-arylpyrazoles exert their activity by being distributed through the sebaceous glands of the animal.
WO-A-87/3781, EP-A-295,117 and EP-A-500,209 describe a class of insecticides which are N-phenyl-pyrazole derivatives. These compounds are given as having activity against a very large number of parasites, including Boophilus microplus, fleas, ticks and lice in fields as varied as agriculture, public health and veterinary medicine. The general teaching of these documents indicates that these insecticidal compounds may be administered via different routes: oral, parenteral, percutaneous and topical routes. Topical administration comprises, in particular, skin solutions (pour-on or spot-on), sprays, drenches, baths, showers, jets, powders, greases, shampoos, creams, etc. The pour-on type skin solutions are designed for percutaneous administration. Example 9 of EP-A-295,117 and Example 291 of EP-A-500,209 describe a pour-on type skin solution containing 15% insecticide and 85% dimethyl sulphoxide, for percutaneous administration of the insecticide. 1-N-arylpyrazole derivatives are known in the art to prevent, treat or control ectoparasite infestation in mammals, such as cats, dogs and cattle.
Amitraz is known in the art as a pesticide and is used to control red spider mites, leaf mites, scale insects and aphids. In animals, amitraz is used to control tick, mites, and lice. Extoxnet http://ace.orst.edu/info/extonet/pips/amitraz.html. However, amitraz is not known in the art to treat fleas Amitraz belongs to the amidine chemical family and has the following structure:
Amitraz is described in U.S. Pat. No. 3,781,355 and U.S. Pat. No. 3,864,497.
Other compounds that are known in the art to treat or control endo- and ectoparasite infestations include milbemycin or avermectin derivatives. The avermectin and milbemycin series of compounds are potent anthelmintic and antiparasitic agents against a wide range of internal and external parasites. The compounds which belong to this series are either natural products or are semi-synthetic derivatives thereof. The structures of these two series of compounds are closely related and they both share a complex 16-membered macrocyclic lactone ring; however, the milbemycins do not contain the aglycone substituent in the 13-position of the lactone ring. The natural product avermectins are disclosed in U.S. Pat. No. 4,310,519 to Albers-Schonberg, et al., and the 22,23-dihydro avermectin compounds are disclosed in Chabala, et al., U.S. Pat. No. 4,199,569. For a general discussion of avermectins, which include a discussion of their uses in humans and animals, see “Ivermectin and Abamectin,” W. C. Campbell, ed., Springer-Verlag, New York (1989). Naturally occurring milbemycins are described in Aoki et al., U.S. Pat. No. 3,950,360 as well as in the various references cited in “The Merck Index” 12th ed., S. Budavari, Ed., Merck & Co., Inc. Whitehouse Station, N.J. (1996). Semisynthetic derivatives of these classes of compounds are well known in the art and are described, for example, in U.S. Pat. No. 5,077,308, U.S. Pat. No. 4,859,657, U.S. Pat. No. 4,963,582, U.S. Pat. No. 4,855,317, U.S. Pat. No. 4,871,719, U.S. Pat. No. 4,874,749, U.S. Pat. No. 4,427,663, U.S. Pat. No. 4,310,519, U.S. Pat. No. 4,199,569, U.S. Pat. No. 5,055,596, U.S. Pat. No. 4,973,711, U.S. Pat. No. 4,978,677, and U.S. Pat. No. 4,920,148.                Avermectins and milbemycins share the same common 16-membered macrocyclic lactone ring; however, milbemycins do not possess the disaccharide substituent on the 13-position of the lactone ring. While many avermectin compounds are known in the art, a representative structure of the class of compounds is as follows:        
where the broken line indicates a single or a double bond at the 22,23-positions;                R1 is hydrogen or hydroxy provided that R1 is present only when the broken line indicates a single bond;        R2 is alkyl of from 1 to 6 carbon atoms or alkenyl of from 3 to 6 carbon atoms or cycloalkyl of from 3 to 8 carbon atoms;        R3 is hydroxy, methoxy or ═NOR5 where R5 is hydrogen or lower alkyl; and        R4 is hydrogen, hydroxy or        
                where R6 is hydroxy, amino, mono- or di-lower alkylamino or lower alkanoylamino.        
The preferred compounds are avermectin Bla/Blb (abamectin), 22,23-dihydro avermectin Bla/Blb (ivermectin) and the 4″-acetylamino-5-ketoximino derivative of avermectin Bla/Blb. Both abamectin and ivermectin are approved as broad spectrum antiparasitic agents.
The structures of abamectin and ivermectin are as follows:
                wherein for abamectin the broken line represents a double bond and R1 is not present and for ivermectin the double bond represents a single bond and R1 is hydrogen; and        R2 is isopropyl or sec-butyl.        
The 4″-acetyl amino-5-ketoximino derivatives of avermectin Bla/Blb has the following structural formula:
                where R2 is isopropyl or sec-butyl.        
The avermectin products are generally prepared as a mixture of at least 80% of the compound where R2 is sec-butyl and no more than 20% of the compound where R2 is isopropyl.
Other preferred avermectins, include emamectin, eprinomectin and doramectin. Doramectin is disclosed in U.S. Pat. No. 5,089,490 and EP 214 738. This compound has the following structure:

In the present formulations, ivermectin and eprinomectin are especially preferred.
A representative structure for a milbemycin is that for milbemycin α1:

An especially preferred avermectin is moxidectin, whose structure is as follows:
The compound is disclosed in U.S. Pat. No. 5,089,490.
Other classes of compound are known to treat endo- and ectoparasites. These classes include benzimidazoles, which are effective against tapeworms, lungworms and roundworms, imidazothiazoles, which are effective against roundworms, tapeworms and lungworms, and the pyrethroids. Examples of benzimidazoles include albendazole (U.S. Pat. No. 3,915,986); fenbenzazole (U.S. Pat. No. 3,954,791), mebendazole (U.S. Pat. No. 3,657,261), oxibenzazole (U.S. Pat. No. 3,574,845) and triclabenzazole (U.S. Pat. No. 4,197,307). An example of an imidazothiazole is levamisole (U.S. Pat. No. 3,529,350).
The pyrethoids are a class of naturally occurring or synthetically derived insecticide. Synthetic pyrethroids include pyrethrin I and pyrethrin II. Synthetic pyrethroids include permethrin (U.S. Pat. No. 4,113,968), resmethrin, and sumithrin (U.S. Pat. Nos. 3,934,023 and 2,348,930).